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network: don't add "no-resolv" if we still need DNS servers from resolv.conf

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It was pointed out here:

  https://bugzilla.redhat.com/show_bug.cgi?id=1331796#c4

that we shouldn't be adding a "no-resolv" to the dnsmasq.conf file for
a network if there isn't any <forwarder> element that specifies an IP
address but no qualifying domain. If there is such an element, it will
handle all DNS requests that weren't otherwise handled by one of the
forwarder entries with a matching domain attribute. If not, then DNS
requests that don't match the domain of any <forwarder> would not be
resolved if we added no-resolv.

So, only add "no-resolv" when there is at least one <forwarder>
element that specifies an IP address but no qualifying domain.
This commit is contained in:
Laine Stump 2017-03-17 12:25:43 -04:00
parent f9144125b8
commit 15b5902db9
8 changed files with 61 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/network/bridge_driver.c
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@ -1085,7 +1085,15 @@ networkDnsmasqConfContents(virNetworkObjPtr network,
virBufferAddLit(&configbuf, "port=0\n");
if (wantDNS && network->def->dns.forwarders) {
virBufferAddLit(&configbuf, "no-resolv\n");
/* addNoResolv should be set to true if there are any entries
* that specify an IP address for requests, but no domain
* qualifier (implying that all requests otherwise "unclaimed"
* should be sent to that address). if it is still false when
* we've looked at all entries, it means we still need the
* host's resolv.conf for some cases.
*/
bool addNoResolv = false;
for (i = 0; i < network->def->dns.nfwds; i++) {
virNetworkDNSForwarderPtr fwd = &network->def->dns.forwarders[i];
@ -1099,11 +1107,15 @@ networkDnsmasqConfContents(virNetworkObjPtr network,
goto cleanup;
virBufferAsprintf(&configbuf, "%s\n", addr);
VIR_FREE(addr);
if (!fwd->domain)
addNoResolv = true;
} else {
/* "don't forward requests for this domain" */
virBufferAddLit(&configbuf, "#\n");
}
}
if (addNoResolv)
virBufferAddLit(&configbuf, "no-resolv\n");
}
if (network->def->domain) {

12
tests/networkxml2confdata/nat-network-dns-forwarder-no-resolv.conf Normal file
View File

@ -0,0 +1,12 @@
##WARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
##OVERWRITTEN AND LOST. Changes to this configuration should be made using:
## virsh net-edit default
## or other application using the libvirt API.
##
## dnsmasq conf file created by libvirt
strict-order
server=/example.com/192.168.1.1
except-interface=lo
bind-dynamic
interface=virbr0
addn-hosts=/var/lib/libvirt/dnsmasq/default.addnhosts

11
tests/networkxml2confdata/nat-network-dns-forwarder-no-resolv.xml Normal file
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@ -0,0 +1,11 @@
<network>
<name>default</name>
<uuid>81ff0d90-c91e-6742-64da-4a736edb9a9c</uuid>
<forward mode='nat'/>
<bridge name='virbr0' stp='on' delay='0'/>
<dns>
<forwarder domain='example.com' addr='192.168.1.1'/>
</dns>
<ip address='192.168.122.1' netmask='255.255.255.0'>
</ip>
</network>

2
tests/networkxml2confdata/nat-network-dns-forwarders.conf
View File

@ -5,11 +5,11 @@
##
## dnsmasq conf file created by libvirt
strict-order
no-resolv
server=8.8.8.8
server=8.8.4.4
server=/example.com/192.168.1.1
server=/www.example.com/#
no-resolv
except-interface=lo
bind-dynamic
interface=virbr0

1
tests/networkxml2conftest.c
View File

@ -137,6 +137,7 @@ mymain(void)
DO_TEST("nat-network-dns-hosts", full);
DO_TEST("nat-network-dns-forward-plain", full);
DO_TEST("nat-network-dns-forwarders", full);
DO_TEST("nat-network-dns-forwarder-no-resolv", full);
DO_TEST("nat-network-dns-local-domain", full);
DO_TEST("dhcp6-network", dhcpv6);
DO_TEST("dhcp6-nat-network", dhcpv6);

11
tests/networkxml2xmlin/nat-network-dns-forwarder-no-resolv.xml Normal file
View File

@ -0,0 +1,11 @@
<network>
<name>default</name>
<uuid>81ff0d90-c91e-6742-64da-4a736edb9a9c</uuid>
<forward mode='nat'/>
<bridge name='virbr0' stp='on' delay='0'/>
<dns>
<forwarder domain='example.com' addr='192.168.1.1'/>
</dns>
<ip address='192.168.122.1' netmask='255.255.255.0'>
</ip>
</network>

11
tests/networkxml2xmlout/nat-network-dns-forwarder-no-resolv.xml Normal file
View File

@ -0,0 +1,11 @@
<network>
<name>default</name>
<uuid>81ff0d90-c91e-6742-64da-4a736edb9a9c</uuid>
<forward mode='nat'/>
<bridge name='virbr0' stp='on' delay='0'/>
<dns>
<forwarder domain='example.com' addr='192.168.1.1'/>
</dns>
<ip address='192.168.122.1' netmask='255.255.255.0'>
</ip>
</network>

1
tests/networkxml2xmltest.c
View File

@ -141,6 +141,7 @@ mymain(void)
DO_TEST("nat-network-dns-hosts");
DO_TEST("nat-network-dns-forward-plain");
DO_TEST("nat-network-dns-forwarders");
DO_TEST("nat-network-dns-forwarder-no-resolv");
DO_TEST("nat-network-forward-nat-address");
DO_TEST("nat-network-forward-nat-no-address");
DO_TEST("8021Qbh-net");